Hydrostatic transmission control with hydraulic follow-up

ABSTRACT

A hydraulic follow-up for use with a hydraulic system placed between a rotating input member and a rotating output member. The hydraulic system is a hydrostatic transmission for driving a tractor, and comprises a hydrostatic pump and a hydrostatic motor driven by the pump. When the hydrostatic pump is angularly shifted with respect to the input member, the shifting is controlled by the hydraulic follow-up, which also shifts the motor in relation to the output member.

United States Patent Ruhl et al.

Sept. 4, 1973 I5 IIYDROSTATIC TRANSMISSION CONTROL WITH HYDRAULICFOLLOW-UP Inventors: Charles A. Ruhl, Wheaton: Edward Meyer, NorthRiverside; Probir K. Chatterjea, Des Plaines, all of Ill. InternationalHarvester Company, Chicago, Ill.

Filed: Mar. 2, 1972 Appl. No.: 231,770

Related US. Application Data [73] Assignee:

3,247,669 4/l966 Hann ..6()/l9X Primary Examiner-Edgar W. GeogheganAtt0rneyFl0yd B. Harman [57] ABSTRACT A hydraulic follow-up for use witha hydraulic system placed between a rotating input member and a rotatingoutput member. The hydraulic system is a hydrostatic transmission fordriving a tractor, and comprises a hydrostatic pump and a hydrostaticmotor driven by the pump. When the hydrostatic pump is angularly shiftedwith respect to the input member, the shifting is controlled by thehydraulic follow-up, which also shifts the motor in relation to theoutput member.

2 Claims, 6 Drawing Figures r 1 OUTPUT i 123 l i i 10.9 t 108 l MOTOR YCONTROL #02 1/ l "l CYLINDER /11 j? i MOTOR I I I FEED 114 13 i l PUMP Ii a K r250 XE f J 0 INPUT I (I I 122 2 6b PUMP PUMP l I FEED CONTROL ABACK CYLINDER I 1 b0 1 17 11 l 59 5 9L .19 I v 1 l (O CONTROLLER 1 l l18 l i 27 l l l 250 \28 i PATENTEDser 4 ms SHEET '4 8F 4 W596 m8 u 5RHwl Xom Natal E. Wfik w Na l m m. A UN mm mN hw 1 MK II I I?) M h W1 H 1mN a 4 Q mw R mN N HYDROSTATIC TRANSMISSION CONTROL WITH HYDRAULICFOLLOW-UP This is a division, of application Ser. No. 97,899, filed Dec.14, 1970 now US. Pat. No. 3,693,503.

This invention relates to a hydraulic follow-up primarily adapted foruse in controlling a hydrostatic transmission in a crawler tractor. Morespecifically, the invention relates to a follow-up system in whichdifferent physical positions of master and slave members producedifferent hydraulic pressures in the hydraulic system, whereby anequalization of hydraulic pressures on the master and slave sides isutilized to stop the shift of the slave member. A novel hydrauliccomparator valve is provided herein for automatically sensing suchequalization and expeditiously stopping the shift.

Prior follow-up systems in many instances have had mechanical follow-upsuch as provided by cables and springs for input and feedback signals.The springs forced the systems to take up a great deal of space. Therealso has been the difficulty of assuring that the springs match oneanother. Considerable difficulty has also been encountered in seals thatwere required because of difference in areas against which hydraulicfluid acted in opposite directions, for example, a piston and attachedrod in one direction and the piston alone in the other direction.Responsiveness has been adversely affected because of friction losses inthe seals.

An object of the present invention is to provide a hydraulic follow-upsystem in which the aforementioned disadvantages and, specifically,mechanical follow-up are avoided. Actually, our comparator valvereferred to controls the follow up hydraulically so as to require nomechanical cables or springs whatever for the feed back.

Other objects will appear from the detailed disclosure that follows.

In the drawings:

FIG. 1 is a schematic view showing the present hy draulic follow-upsystem employed in conjunction with a hydrostatic pump, a hydrostaticmotor, and rotating input and output members connected thereto;

FIG. 2 is a sectional view of the portion of FIG. 1 enclosed in thedotted outline II and showing a manual controller;

FIG. 3 is a sectional view of the portion of FIG. 1 enclosed in thedotted outline III and showing a pump valve and a motor valve;

FIG. 4 is a sectional view of the portion of FIG. 1 enclosed in thedotted outline IV and showing the output member, the motor, amotor-control cylinder, and a motor feedback;

FIG. 5 is a sectional view of the portion of FIG. 1 enclosed in thedotted outline V and showing the input member, the pump, a pump-controlcylinder, and a pump feedback; and

FIG. 6 is a showing of a block diagram, as an aid to visualize adaptingthe invention to be embodied in a track type tractor.

As shown in FIG. 1, a rotating input member 10 connected to the engineof a tractor drives a hydrostatic pump 11. The pump has a tilting headand is connected by lines 13 and 14 for driving a hydrostatic motor 15.The motor has a tilting head and drives a rotating output member 16. Theinput member 10 and pump 11 are so connected that when they are aligned,as shown in FIG. 1, the pump 11 delivers no fluid. When, however, thehead of the pump 11 is angled with respect to the input member 10, thepump in well known way delivers hydraulic fluid through the line 13 tothe motor 15, causing it to rotate. The motor 15 and output member 16are so arranged and connected with one another that the ratio of thespeed of the output member 16 to that of the motor 15 is increased asthe head of the motor 15 is moved toward axial alignment with the outputmember 16. One purpose of the apparatus of the present invention is toadjust the angle of the pump 11 with respect to the input member 10 and,in addition, to make the angle of the motor 15 with respect to theoutput member 16 dependent upon the angle of the pump 11 with respect tothe input member 10.

As shown in FIG. 2, a controller 17 is provided with comprises amanually adjustable inner member 18 and a stationary outer member 19tightly enclosing the inner member 18. The inner member 18 has a wideannular external peripheral groove 20 and two narrow shallow externalhelical grooves 21 and 22 extending from the ends of the groove 20. Theend of the helical groove 22 away from the groove 21) terminates at oneend of the inner member 18. The end of the helical groove 21 away fromthe annular groove 20 terminates at a reduced portion 23 formed on theinner member 18. The reduced portion 23 has a cross passage 24 which isconnected with a longitudinal passage 25 in the inner member 18extending to the end of the inner member 18 adjacent the end of thehelical groove 22. A line 26 leading from a source of hydraulic fluidunder pressure, for example, about 250 lbs. per square inch, isconnected to the outer member 19 so as to be'in communication with theannular groove 20 on the inner member 18 in its various positions. Lines27 and 28 are connected to internal annular peripheral grooves 29 and30, respectively, which are on opposite sides of and in spaced relationto the connection with the line 26. The grooves 29 and 311 arepositioned so as to lie beyond the ends of the helical grooves 21 and22, respectively, away from the groove 20 when the inner member 18 is inthe central position of FIG. 2. When the inner member 18 is shifted fromits central position, the groove 29 or 30 overlaps an intermediateportion of the helical groove 21 or 22. Each of the helical grooves 21and 22 and the interior of the outer member 19 forms a restrictedorifice of appreciable length.

VALVE 31, COMPARATOR FIGS. 1 AND 3 As shown in FIG. 1, the lines 27 and23 lead from the outer member 19 of the controller 17 to a controlapparatus or valve 31 for the pump 11, and more particularly, as shownin FIG. 3, to a housing 32 of the valve 31 near its ends. The housing 32has a central longitudinal bore 33, a passage 34 leading by a line 35 toa source of hydraulic fluid under pressure, for example, 700 to 900 lbs.per square inch, a pair of delivery passages 36 and 37, and a pair ofdrain passages 38 and 39. The passages 34, 36, 37, 38, and 39 areconnected with the central bore 33 by means of annular grooves 40, 41,42, 43, and 44, respectively. The housing 32 has at the end where theline 28 is connected, a space 45, which is located beyond one end of thebore 33 and comprises a large near chamber 46 and a first, small farchamber 47, which are, respectively, near to and spaced fromhousing 32has at the end at which the line 27 is con nected a space 48 which liesbeyond the other end of the bore 33. The space 48 is formed of a largenear chamber 49 and a second small far chamber 50, the

chamber 49 being adjacent the said other end of the bore 33 and enlargedin relation thereto, and the second, small chamber 50 being spaced fromthe said other end of the bore 33 and reduced in relation to the chamber49. The lines 27 and 28, respectively, are connected with the largechamber 49 of the space 48 in the housing 32 and with the large chamber46 of the space in the housing.

A movable, pressure comparator member 51 is mounted in the housing 32and comprises a valve spool, provided with two end lands 52 and acentral land 53 spaced from the end lands by reduced portions 54. Beyondthe end lands 52, the movable portion 51 has reduced extensions 55 whichproject into the large chambers 46 and 49 of the spaces 45 and 48. Apair of collars 56 is provided, one being located in the large chamber46 so as to be engageable with the end thereof adjacent the bore 33 andwith a shoulder formed at the juncture of the adjacent extension 55 withthe associated end land 52, the other collar 56 being located in thelarge chamber 49 so as to be engageable with the end thereof adjacentthe bore 33 and with a shoulder formed at the juncture of the adjacentreduced extension 55 with the associated end land 52. A pair of springs57 is located in the large chambers 46 and 49 (sometimes referred tohereinafter as the third and fourth chambers, respectively) so as to actagainst the ends thereof adjacent the respective first and second smallchambers 47 and and against the collars 56.

A pair of pistons 58 is provided, one being located in the small chamber47 so as to separate it from the large chamber 46, the other pistonbeing located in the small chamber 59 so as to separate it from thelarge chamber 49. The pistons 58 are engageable with the extensions onthe movable member 51. The ends of the pistons 58 engaging theextensions 55 are chamfered as are the ends of the extensions 55. Thepistons 58 have the same diameter as the lands 52 and 53.

The delivery passages 36 and 37 in the housing 32 are connected withdelivery lines 59 and 590, respectively, which, as shown in FIGS. 1 and5, are connected to opposite ends of a pump control cylinder 60 atopposite sides of a piston 61 slidably mounted in the cylinder 60. Apiston rod 62 is secured to the piston 61 and projects through the endsof the cylinder 60. One end of the piston rod 62 is connected through alink 63 with a pivotal arm 64, which controls the angle of the pump 11with respect to the input member 10. The end of the piston rod 62opposite that connected to the arm 64 abuts an inner member 65 of a pumpfeedback device 66, which also includes an outer member 67 tightlyenclosing the inner member 65. The inner member 65 has a. wide annularperipheral groove 68 and two narrow shallow helical grooves 69 and 70extending from the ends of the groove 68 to the ends of the inner member65. Each of the helical grooves 69 and 70 and the interior of the outermember 67 forms a restricted orifice of appreciable length. The outermember 67 has a wide internal annular peripheral groove 71 which remainsin overlapping engagement with' groove 68 of the inner member 65 invarious positions of the inner member.

A line 72 connects the groove '71 with a source of hydraulic fluid underpressure, for example, at 150 lbs.

per square inch. The outer member 67 has internal annular peripheralgrooves 73 and 74 which lie on opposite sides of the groove 71 andcommunicate with the helical grooves 69 and 70 of the inner member 65.Beyond the grooves 73 and 74 there are connections 75 and 76 to drain. Aspring 77 which maintains the inner member 65 in engagement with thepiston rod 62 acts between the ends of the inner member 65 and the endof the outer member 66 away from the piston rod 62. Lines 78 and 79,respectively, connect the annular grooves 74 and 73 in outer member 67with small chambers 50 and 47 in valve housing 32, as shown in FIGS. 1,3, and 5.

VALVE 80. COMPARATOR FIG. 3

As shown in FIG. 3, a motor valve 80 comprises a housing 81 and amovable, pressure comparator member 82 shiftably mounted in a centrallongitudinal bore 83 in the housing 81. The movable member 82 is a valvespool, provided with two end lands 84 and a central land 85 spaced fromone another by reduced portions 85a. The movable member 82 also has atits ends reduced extensions 86, one of which projects into a chamber 87forming part of a space 88 in the body 81, and the other into a chamber89 forming part of a space 90 in the body 81. The spaces 88 and 90 alsoinclude chambers 91 and 92, respectively. The chambers 87 and 89 areadjacent the ends of the bore 83, are enlarged with respect thereto, andso may be described as large near chambers. The chambers 91 and 92 arespaced from the ends of the bore 83, are reduced in re lation to thechambers 87 and 89, respectively, and so may be described as small farchambers. Pistons 93, which are located in the chambers 91 and 92 of thespaces 88 and 90, separate chamber 91 from chamber 87 and chamber 92from chamber 89. The pistons 93 have the same diameter as the lands 84and 85 of the member 82. The ends of the pistons 93 engaging theextensions 86 are chamfered, as are the ends of the extensions.

A central annular internal peripheral groove 94 formed on the bore 83 inthe body 81 is connected by a line 95 and the groove 40 in the housing32 with the high-pressure line 35. At opposite sides of the groove 94 inspaced relation thereto, annular peripheral grooves 96 and 97 are formedin the central bore 83 of the housing 81 and are connected to drainthrough the lines 38 and 39, respectively. At opposite sides of thegroove 94 and between the same and the grooves 96 and 97, annularperipheral grooves 98 and 99 are formed on the central bore 83 and, asshown in FIG. 4, are connected by lines and 101, respectively, with amotor-control cylinder 102 near its ends and at opposite sides of apiston 103 slidably mounted in the cylinder 102.

Again with reference to FIG. 3, the small chamber 91 of the space 88 isconnected by a line 104 with drain. Two collars are provided, one collarbeing engageable with the end of the large chamber'87 adjacent the bore83 and with a shoulder formed between one reduced extension 86 and theadjacent land 84 of the movable member 82, the other collar 105 beingengageable with the end of the large chamber 89 adjacent the bore 83 andwith a shoulder formed between the other reduced extension 86 and theadjacent land 84. The collars 105 are urged against the parts just described by springs 106 which act between the collars 105 and the ends ofthe large chambers 87 and 89 away from the bore 83. The small chamber 92is connected by a line 107 with the line 27. The large chamber 89 isconnected with the line 27 by a line 107a and the large chamber 49 inthe valve housing 32.

As shown in FIG. 4, the piston 103 is secured to a rod 108 one end ofwhich projects beyond one end of the cylinder 102 and is connected witha link 109 which is in turn connected with a pivotal arm 110, whichcontrols the angle of the motor with respect to the output member 16.The other end of the piston rod 108 projects from the other end of thecylinder 102 into an outer member 11 and into engagement with one end ofan inner member 112 slidably mounted in the outer member 111. Themembers 111 and 112 and a spring 113 constitute a motor feedback device114. The spring 112a which acts between the end of the inner member 112remote from the piston rod 108 and a closed end of the outer member 111remote from the cylinder 102, maintains the inner member 112 inengagement with the piston rod 108. The space in the outer member 111where the spring 113 is located is connected to drain.

The inner member 112 is provided with a centrally located narrow shallowhelical groove 118 and two wide external peripheral annular grooves 119and 120 into which the ends of the helical groove 118 open. The helicalgroove 118 and the interior of the outer member 111 form a restrictedorifice of appreciable length. The annular groove 119 is connected witha source of hydraulic fluid under some intermediate pressure such as 250lbs/in. by a line 121 connected with the outer member 111. The annulargroove 120 is connected with a source of hydraulic fluid under somelower intermediate pressure such as l50 lbs/in. by a line 122 connectedwith the outer member 111. A line 123 connects the large chamber 87 inthe housing 81 with an annular peripheral groove 124, which is locatedin the interior of the outer member 111 between the spaced from theregions at which the lines 121 and 122 are connected. The groove 124 isoverlapped by an intermediate region of the helical groove 118 on theinner member 112 or the annular groove 120 or both the groove 120 andthe adjacent end region of the helical groove 118, depending on theposition of the member 112 in the piston 103 in the cylinder 102.

This two-path hydrostatic transmission has settings providing lo-hiranges forward and rearward as follows.

FORWARD RANGES (2) In the transmission setting providing a lo-forwardspeed range, the motor head 15 is fixed at a large acute angle fromstraight or flat alignment axially and the pump head 11 varies from azero or flat angle corresponding to zero pumping and zero vehicle speedto a large forward acute angle corresponding to maximum forward pumpoutput. The motor being forwardly driven thereby'runs at half speed moreor less at the highest.

In the setting providing a hi-forward range, the head angle of the pump11 is fixed at the large forward acute angle corresponding to maximumforward pump output. The motor head angle varies from the large acuteangle corresponding to about half speed to a small acute anglecorresponding to full forward speed at full pump output.

REARWARD RANGES 2) In the setting providing a lo-rearward speed range,the motor head 15 is fixed at a large acute angle from straight or flatalignment and the pump head angle varies from a zero or flat anglecorresponding to zero pumping and zero vehicle speed to a large acuteangle corresponding to maximum rearward pump output. The motor beingdriven rearwardly thereby runs at half speed more or less at thehighest.

In the setting providing a hi-rearward range, the pump head angle isfixed at the large acute angle corresponding to maximum rearward pumpoutput. The motor head angle varies from a large acute angle to a smallacute angle corresponding to full speed rearwardly at full pump output.

SERVO STRUCTURE PER SE In respect of the essentials for a basicservosystem per se, the mechanisms provided are a compound followervalve 66 (FIG. 1) having a source of high and low pressure, hydraulichead setting mechanism 60 causing the valve to take an actual speedposition corresponding to the angular position of the tilting pump head1 1, a second compound valve 19 having a source of high and lowpressure, manual mechanism 18 to move the second valve to a desiredspeed position corresponding to the angular position of the manualmechanism 18, and a pressure movable comparator means 31 in the outputof the valves hydraulically disposed to operate the hydraulic mechanism60 to a point at which the outputs reach a balance indicative ofcorrespondence in angular position between the manual mechanism 18 andthe hydraulic mechanism 60.

SERVO STRUCTURE TWO RANGES In order to move the tractor through tworanges of speed in each direction, the mechanisms provided consist ofthe foregoing pump control system including the compound follower valveand the compound second valve for a two directional operation, plusessentially the same system for the motor except including merely asimple follower valve and simple second valve for such motor.

SERVO STRUCTURE BOTH SIDES Steering by driving is accomplished byoperating the two tracks of a tractor at differing speeds. In order toproduce differing speeds, mechanism provided at one side is a duplicateof the mechanism provided at the other side and each will consist of apump at the side with the endless track at that side, a drive motormechanically connected to the track and hydraulically connected to thepump, and the necessary servo structure of the foregoing character foreach of the pump and the motor. A splitter box transmits power to therespective pumps at the sides of the tractor from a common tractorpropulsion engine.

SPLITTER BOX FIG. 6

The tractor engine, according to the showing of this Figure, is coupledin common to the FIG. 1 systems through the splitter box.

LO-FORWARD SPECIFICALLY Reference is now made to FIG. 2. The pressuresin the lines 27 and 2% are dependent on the pressure in the line 26 andon the positions of overlap of the helical grooves 21 and 22 with theannular grooves 29 and 30 connected to the lines 27 and 28. The pressurealong the helical grooves 21 and 22 each of which combines with theouter member 19 to form a restricted orifice of appreciable length, aspreviously stated, varies from the intermediate pressure of about 250lbs/in. existing in the line 26 and the drain pressure. Thus, thepressure in each of the grooves 21 and 22 varies from a maximum at theend thereof at the wide annular groove 20 to a minimum at the end of thehelical groove 21 or 22 away from the groove 20. So, the pressureexisting in the line 27 or 28 depends on how far along the helicalgroove 21 or 22 the groove 29 or 30 is located with reference to thewide annular groove 20. Thus, when the inner member 18 is centrallylocated in the outer member 19, the pressure in the lines 27 and 28 areequal, with the result that equal pressures exist in the chambers 46 and48 at the ends of the housing 32. Consequently, when as shown in FIG. 3,the lands 52 and S3 overlap the grooves 43 and 44 connected with thedrain lines 38 and 39 and the groove 46) connected with the pressureline 35, flow to and from the delivery lines 58 and 59 isblocked and thepiston 61 is maintained in a central position in the cylinder 60, withthe result that the pump 11 is aligned with respect to the input memberand thus delivers no fluid to the motor 15.

When the inner member 18 is moved with respect to the outer member 19 tothe right of the position shown in FIG. 2, the line 27 is at drainpressure, and line 28 is at a higher pressure between drain pressure andthat of line 26. This is due to the fact that the groove 29 connected tothe line 27 is overlapped by reduced portion 23 of the inner member 18connected by passages 24 and 25 to drain, and that the groove 30connected to the line 28 is overlapped by a portion of the helicalgroove 22 intermediate its ends. The movable member 51 now movesdownwards as viewed in FIG. 3, with respect to the housing 32 downwardsas viewed in FIG. 3, from the position of FIG. 3, because the pressurein the chamber 46 is higher than that in chamber 49 and also than thatin chamber 50, which is at drain pressure because of the centralposition of the member 65, as shown in FIG. 5. Downward movement of themovable member 51 from the position of FIG. 3 makes the middle land 53and the lower end land 52 uncover groove 40 and groove 42, respectivelyin such a fashion that the delivery line 59 is connected to the pressureline 35 and the delivery line 590 with the drain line 39.

Thus, the piston 61 moves in cylinder 60 to different points to theright as veiwed in FIG. 5, from the position of FIG. 5, causing the pumpill to move to positions to and including various displacement settingsincluding the lower phantom position of FIG. 5, with the result thatpressure fluid is supplied to and from the motor to the lines 13 and 14so as to make the motor 15 drive the output member 16 at actual speedsin a direction that may, for convenience, be termed forward." As thepiston 61 moves to the right and takes along the piston rod 62, thespring 77 makes the inner member 65 also move to the right of theposition shown in FIG. 5. The result is that the annular groove 74 ofthe outer member 67 in effect moves along the helical groove 70 in adirection toward the annular groove 68 which is under the pressure ofthe fluid supplied by the line 72. Consequently, the pressure in line 78and chamber 50 in the housing 32 increases to that existing in thechamber 46. So the movable member 51 is shifted back up to the positionof FIG. 3 in which flow to and from the delivery lines 59 and 59a andthe cylinder 60 is blocked so that the piston 61 and the pump 11 are forthe moment fixed against further movement.

For various positions to the right of that shown in FIG. 2 for the innermember 18, there are various positions of the piston 61 to the right andthe pump 11 downward from the full-line position shown in FIG. 5,because as the member 18 moves farther to the right, the pressure inline 28 continues to rise, becuae the groove 30 overlaps a portion ofthe helical groove 22 closer to the end at the annular groove 20. Theincreased pressure in the chamber 46 in the housing 32 necessitates anincreased balancing pressure in the chamber 50 in the housing 32. Theincreased pressure in chamber 50 can result only from a movement of themember 65 to the right causing the overlap between annular groove 74 andhelical groove 70 to occur at a region of the helical groove closer tothe annular groove 6%. This can occur only with rightward movement ofthe piston 61 and downward movement of the pump 11.

The angled position of the pump 11 with respect to the input member 10is limited by a stop (not shown), and so the rightward position of thepiston 61 in the inner member 65 is also limited. This means that if themember 18 is moved to the right farther than that required for movingthe pump l1 down to the final phantom position limited by the stop, thepressure in the chamber 50 in the housing 32 will not increase to thatin the chamber 46, and so the movable member 51 stays down from theposition of HG. 3, with the result that the groove 40 in the housing 32continues unblocked by the central land 53.

The pressure in chamber 92 of housing 81 of motor valve is, of course,equal to that in pressure line 28 because of the line 107 connectingchamber 92 with line 28. So as the inner member 18 continues to move tothe right as viewed in FIG. 2 to bring line 28 to a pressure approachingthat in line 26, the pressure in chamber 72 of motor valve 80 can, byapproaching the 250 lbs. in line 26, surpass that in chamber 87, whichis at the I50 lbs. existing in line 122. At the outset and during theearly movement of the inner member 18 to the right, as viewed in FIG. 2,the line 28 is, of course,

at or near drain pressure, as is chamber 92, connected 1 by line 367with line 28, and so the greater pressure in chamber 87 holds themovable member 82 of motor valve 80 in the position in FIG. 3. In thisposition of member 82, the piston 103 is in the position of FIG. 4,because the cylinder 102 above piston 103 is connected withhigh-pressure line 35 through groove 40 in pump valve 31, line 95,groove 94 in the motor valve 80, reduced portion 86, groove 98, and line100, and the cylinder 102 below piston 103 is connected to drain throughline 101, groove 99 in motor valve 80, reduced portion 86, groove 97,and line 39. As a result, the motor 15 stays while in the lo-forwardrange always at a maximum angle represented by the full-line position ofFIG. 4, for example, 35. A stop (not shown) at the motor 15 limits itsmaximum angle and acts through arm illO, link 109, and piston rod 108 tolimit piston 103 to the position shown.

iii-FORWARD SPECIFICALLY When, as mentioned, the pressure in chamber 92becomes greater than that in chamber 87, the movable member 82 of themotor valve 80 moves upward as viewed in FIG. 3, reversing the positionof central land 85 with respect to groove 94 and the connections oflines 100 and 101 to drain and pressure fluid. The result is that thepiston 103 moves upward as viewed in FIG. 4 and acts through the pistonrod 108, link 109, and arm 110 to reduce the angle of the motor withrespect to the output member 16 and bring the motor to or toward thephantom position which is limited by a stop (not shown). The minimumangle of the motor 15 may be 19 for example. These progressive decreasesin the angle of the motor 15 result in proportionate increases in speedof the output member 16 throughout the hi-forward range, because of theway in which the motor 15 operates. As the piston 103 moves upward inthe cylinder 102, the spring 113 makes the member 112 follow the pistonrod 108 upward. In effect, the annular groove 124 and line 123 are movedalong the helical groove 119 toward the end thereof connected with therelatively high intermediate pressure in line 121 by way of the reducedportion 119.

The result is that the pressure in the line 123 and the chamber 87increases from the 150 lbs. existing in the line 122 toward the 250 lbs.existing in line 120. When a balance is achieved in the pressures inchambers 87 and 92, the movable member 82 is brought back to anintermediate position in which the lands 84 and land 85 completelyoverlap grooves 96 and 97, groove 94, respectively, and so flow to andfrom the cylinder 102 in the lines 100 and 101 is blocked, with theresult that the piston 103 and motor 15 are fixed in position. This isthe way in which some angle of motor 15 between the maximum and minimumangles is achieved. The minimum angle of the motor 15 is determined by astop as previously described, and at the minimum angle the shift ofhelical groove 118 with respect to groove 129 and line 123 may be suchas to provide a pressure in chamber 87 equal to that in chamber 92.

If the inner member 18 is moved to the left, back toward the positon ofFIG. 2, the groove in the outer member 19 is moved relative to thehelical groove 22 away from the high-pressure end thereof so that thepressure in line 28 and chamber 92 of the motor valve 80 is loweredbelow that in chamber 87. The result is that the motor valve 80 is movedback toward the position of FIG. 4, causing the line 101 to be connectedto drain and line 100 to be connected to the pressure line by way ofgrooves 40 and 98 in line 95. As a consequence, the piston 103 moves soas to increase the angle of the motor 15 with respect to the output mem'ber 16. Such movement of the piston 103 also moves the helical groove118 on the inner member 112 along annular groove 124 and line 123 so asto lower the pressure in chamber 87. Downward movement of the innermember 112 causes the pressure in line 123 and the chamber 87 at the topof the movable member 82 of the motor valve 80 to be lowered toward thatpressure existing in line 122.

If a pressure balance is thereby achieved between the chamber 87 at thetop of the movable member 82, and the pressure in the chamber 92 at thebottom of the movable member 82, the movable member 82 is returned tothe position in which it blocks flow into and out of the cylinder 102via the lines 100 and 101 and holds piston 103 and motor 15 againstmovement. Thus, downward movement of the piston 103 and the associatedmovement of the motor back toward the full-line position of FIG. 4occur. When sufficient movement of the inner member 18 back toward theposition of FIG. 2 occurs, the pressure in the chamber 92 falls belowthe minimum pressure of about 150 lbs. in the chamber 87 as determinedby line 122. The movable member 82 of motor valve 80 assumes theposition of FIG. 3 and stays there. As a result, lines 100 and 101,respectively, stay connected to high-pressure line 35 and drain, piston103 stays in the position of FIG. 4, and the motor 15 in the full-lineposition of FIG. 4.

Let us now consider how movement of the inner member 18 to the lefttoward the position of FIG. 2 affects pump 11. Leftward movement ofinner member 18 reduces pressure in line 28 and chamber 46 of pump valve46 below that in chamber 50, and so the movable member 51 moves upwardas viewed in FIG. 3, connecting delivery line 59 to drain and deliveryline 59a to the pressure line 35. The result is that the piston 61 andinner member 65 move to the left as viewed in FIG. 5, causing thehelical groove to shift with respect to the annular groove 74, with theresult that a lower pressure is achieved in groove 74 as well as inchamber 50, connected with groove 74 by line 78. When the pressure inchamber 50 is lowered to that in chamber 46, the movable member 51returns to the position of FIG. 3, causing the delivery lines 59 and 59ato the cylinder 60 to be blocked. Thus, the piston 61 and the pump 11are again fixed in position, the new position of the pump 11 involvingless angle with respect to the input member 10.

LO-REARWARD SPECIFICALLY In case the drive of the output member 16 is tobe reversed with respect to the input member 10, the inner member 18 ismoved leftward from the neutral position of FIG. 2. In that case, theline 28 is at drain pressure, since the annular groove 30 at the time isat or beyond the end of the helical groove 22 remote from the annulargroove 20. At the same time, the pressure in the line 27 is increased,because in effect the annular groove 29 connected with the line 27 ismoved along the helical groove 21 toward the end thereof at the annulargroove 20. The result is that the pressure in chamber 49 at the lowerend of the movable member 51 is increased, resulting in upward movementof the movable member 51 to a position in which the delivery line 58 isconnected through the groove 43 and line 38 to drain, and the deliveryline 59 is connected to the pressure line 35. The result is leftwardmovement of the piston 61 and the cylinder and movement of the pump 11from the aligned full-line position of FIG. 5 to or toward the upperangled position of FIG. 5. As the piston 61 moves to the left, thepiston rod 62 moves the member 65 to the left, in effect causing thegroove '73 to overlap a portion of the helical groove 69 nearer theannular groove 68. The result is an increase in pressure in the line 79and the chamber 47 at the upper end of the movable member 51. When abalance is achieved in the chambers 47 and 50, the movable member 51returns to the blocking position of FIG. 3, and further leftwardmovement of the piston 61 is stopped.

I-llI-REARWARD SPECIFICALLY In the operation of the motor valve 80 inreverse drive, the chamber 89 functions as does the chamber 92 inforward drive. The chamber 89 is connected to the line 27 through theline l07a and chamber 49. When the inner member 18 moves sufficiently tothe left as viewed in FIG. 2, the movement of the helical groove 21along the annular groove 29 increases the pressure in line 27 andchamber 89 of motor valve 80 until said pressure surpasses that inchamber 87. The result is movement of the member 82 of motor valve 80upward as viewed in FIG. 3 from the position of FIG. 3 so that thepressure and drain connections to lines 100 and 101 are reversed, thepiston 103 moves upward as viewed in FIG. 4 from the position shown, andthe angle of the motor with respect to the output member 16 isdecreased.

The remainder of the drive and control for a reverse direction ofoperation may be understood in reference to what has already been setforth in regard to a forward direction. Forward drive of the motor 15and output member 16 is achieved by an angling of the pump 11 in onedirection from alignment with the input member, whereas reverse drive ofthe motor 15 and output member 16 is achieved by angling of the pump inthe other direction. Both for forward drive and for reverse drive, themotor 15 is angled in only one direction from alignment with the outputmember 16. The angling of the pump 11 in the two directions from theposition of alignment shown, these positions being shown by the phantomlines in FIG. 5, is achieved by the two helical grooves 21 and 22, asshown in FIG. 2, at opposite sides of the wide groove 20 on the movableshift member 18; two helical grooves 69 and 70, as shown in FIG. 5, atthe opposite sides of the annular groove 68 on the movable member 65 inthe follow-up or feedback device 65; four chambers 46, 47, 49, and 50 asshown in FIG. 3, at the ends of the housing 32; and the two pistons 58which, as shown in FIG. 3, are separate from the reduced extensions 55at the ends of the movable member 51 so as to move away from the movablemember 51 in one condition of operation and to move toward it in theother condition.

An important feature of the present invention is the various restrictedorifices of appreciable length such as those formed by the helicalgrooves 21 and 22 in the interior of the outer member 19, as shown inFIG. 2, those formed by the helical grooves 69 and 70 in the interior ofthe'outer member 67, as shown in FIG. 5, and that formed by the helicalgroove 118 in the interior of the outer member 111. The significantthing about these restricted orifices of appreciable length is that thepressure of the fluid flowing through the orifices varies considerablyfrom one end of each orifice to the other, because it is restricted andlong.

Moreover, there is a special advantage in forming each orifice with thehelp of a helical groove. The length of the helical groove is a multipleof the length of the portion of the member on which the helical grooveis formed. So there need be only a relatively small longitudinalmovement of said member with respect to its associated member to producea relatively big movement along the helical groove of the pressuretakeoff point. Thus, a little movement of the grooved member can producea big change in pressure.

There are special advantages in the control apparatus or valve 31 forthe hydrostatic pump 11. This apparatus 31 is adapted for use with thecontroller 17 of FIG. 2 having two helical grooves 21 and 22 forming tworestricted orifices as well as the pump feedback 66 of FIG. 5 having twohelical grooves 69 and '70 also forming two restricted orifices, becauseapparatus 31 has two pistons 58 operating with inner member SI providingfour end chambers 36, 47, 49, and 50 in the housing 32. Thus, there arethe two chambers 36 and 49 at the ends of the housing 32 having thepressures at the takeoff points in the helical grooves 21 and 22 foropening the pump valve 31, and two chambers 47 and 50 at the ends of thehousing 32 having the pressures of the grooves 69 and 70 for closing thevalve. This means that there can be both forward and reverse operationof the pump 11 produced by the positioning of the pump in the phantompositions shown above and below the full-line position in FIG. 5.

It is understood that the system of control disclosed in the presentapplication is equally adaptable to a motor and pump either or both ofwhich are swashplate type apparatus provided for driving one side of aso-called crawler tractor, a similar apparatus and control system beingprovided for driving the other side.

What is claimed is:

1. In an assembly in which an adjuster acting between a pump and adriving part therefor is associated with a pair of pressure chambers soas to provide for a pressure imbalance of a given sign between thepressure chambers to increase the driving ratio of driving part to pump,a pressure imbalance of the opposite sign to decrease said drivingratio, and a pressure balance to fix said driving ratio; and anotheradjuster acting between a motor driven by the pump and a driven partdriven by the motor is associated with another pair of pressure chambersso as to provide for a pressure imbalance of one sign between thelast-named chambers to increase the driving ratio of motor to drivenpart, a pressure imbalance of the opposite sign to decrease thelast-named driving ratio, and a pressure balance to fix the last namedratio;

the combination with the said adjusters, of

a. means forming first, second, and third restricted orifices ofappreciable length;

b. means connecting one end and the other end of each of the first andsecond orifices to an intermediate fluid pressure and to drain pressure,respectively, for flowing pressure fluid through the first and secondorifices;

c. means connecting one end and the other end of the third orifice tohigh fluid pressure and to intermediate fluid pressure for flowingpressure fluid through the third orifice;

d. means for adjustably connecting one pressure chamber associated withthe adjuster for the pump and one pressure chamber associated with theadjuster for the motor with various points along the first orifice;

e. means for adjustably connecting the other pressure chamber associatedwith the pump adjuster with various points along the second orifice;

f. means for causing adjustment of the driving ratio between drivingpart and pump to act against the last-named means;

g. means for adjustably connecting the other pressure chamber associatedwith the motor adjuster to various points along the third orifice; and

b. means for causing adjustment of the driving ratio between the motorand the driven part to act against the last-named means.

2. In an assembly in which a rotating driving part drives a hydrostaticpump by virtue of an angle between the axes of the driving part and thepump; a piston-and-cylinder unit for the pump controls the angle betweenthe axes of the pump and driving part and is controlled by a valveoperated by opposed pressure chambers; a hydrostatic motor ishydraulically driven by the hydrostatic pump; a rotating driven part isdriven by the hydrostatic motor by virtue of the angle between the axesof the motor and the driven part and operates faster with a decrease inthe last-named angle; and a piston-and-cylinder unit for the motorcontrols the last-named angle and is controlled by a valve operated byopposed pressure chambers;

the combination with the piston-and-cylinder units and the valves, of

a. means forming first, second, and third restricted orifices ofappreciable length;

b. means connecting one end and the other end of each of the first andsecond orifices to an intermediate fluid pressure and to drain pressure,respectively, for flowing pressure fluid through the first and secondorifices;

0. means connecting one end and the other end of the third orifice tohigh fluid pressure and to intermediate fluid pressure for flowingpressure fluid through the third orifice;

(1. means for adjustably connecting one pressure chamber of the valvefor the pump and one pressure chamber of the valve for the motor withvarious points along the first orifice;

e. means for adjustably connecting the other pressure chamber of thepump valve with various points along the second orifice;

f. means for causing relative adjustment of the psiton and cylinder ofthe unit for the pump to act against the last-named means;

g. means for adjustably connecting the other pressure chamber of themotor valve with various points along the third orifice; and

h. means for causing relative adjustment of the piston and cylinder ofthe unit for the motor to act against the last-named means.

1. In an assembly in which an adjuster acting between a pump and adriving part therefor is associated with a pair of pressure chambers soas to provide for a pressure imbalance of a given sign between thepressure chambers to increase the driving ratio of driving part to pump,a pressure imbalance of the opposite sign to decrease said drivingratio, and a pressure balance to fix said driving ratio; and anotHeradjuster acting between a motor driven by the pump and a driven partdriven by the motor is associated with another pair of pressure chambersso as to provide for a pressure imbalance of one sign between thelastnamed chambers to increase the driving ratio of motor to drivenpart, a pressure imbalance of the opposite sign to decrease thelast-named driving ratio, and a pressure balance to fix the last namedratio; the combination with the said adjusters, of a. means formingfirst, second, and third restricted orifices of appreciable length; b.means connecting one end and the other end of each of the first andsecond orifices to an intermediate fluid pressure and to drain pressure,respectively, for flowing pressure fluid through the first and secondorifices; c. means connecting one end and the other end of the thirdorifice to high fluid pressure and to intermediate fluid pressure forflowing pressure fluid through the third orifice; d. means foradjustably connecting one pressure chamber associated with the adjusterfor the pump and one pressure chamber associated with the adjuster forthe motor with various points along the first orifice; e. means foradjustably connecting the other pressure chamber associated with thepump adjuster with various points along the second orifice; f. means forcausing adjustment of the driving ratio between driving part and pump toact against the last-named means; g. means for adjustably connecting theother pressure chamber associated with the motor adjuster to variouspoints along the third orifice; and h. means for causing adjustment ofthe driving ratio between the motor and the driven part to act againstthe last-named means.
 2. In an assembly in which a rotating driving partdrives a hydrostatic pump by virtue of an angle between the axes of thedriving part and the pump; a piston-and-cylinder unit for the pumpcontrols the angle between the axes of the pump and driving part and iscontrolled by a valve operated by opposed pressure chambers; ahydrostatic motor is hydraulically driven by the hydrostatic pump; arotating driven part is driven by the hydrostatic motor by virtue of theangle between the axes of the motor and the driven part and operatesfaster with a decrease in the last-named angle; and apiston-and-cylinder unit for the motor controls the last-named angle andis controlled by a valve operated by opposed pressure chambers; thecombination with the piston-and-cylinder units and the valves, of a.means forming first, second, and third restricted orifices ofappreciable length; b. means connecting one end and the other end ofeach of the first and second orifices to an intermediate fluid pressureand to drain pressure, respectively, for flowing pressure fluid throughthe first and second orifices; c. means connecting one end and the otherend of the third orifice to high fluid pressure and to intermediatefluid pressure for flowing pressure fluid through the third orifice; d.means for adjustably connecting one pressure chamber of the valve forthe pump and one pressure chamber of the valve for the motor withvarious points along the first orifice; e. means for adjustablyconnecting the other pressure chamber of the pump valve with variouspoints along the second orifice; f. means for causing relativeadjustment of the psiton and cylinder of the unit for the pump to actagainst the last-named means; g. means for adjustably connecting theother pressure chamber of the motor valve with various points along thethird orifice; and h. means for causing relative adjustment of thepiston and cylinder of the unit for the motor to act against thelast-named means.